FASTING CONFINEMENT EFFECTS ON SHARKS 613 



indicated on calibrated gauges. Frozen sections of interrenal tissue (20 /am) 

 were floated on 3% hydrogen peroxide, as in the Schultz technic (Thomas 

 1966). After 3 min, a section was transferred to an acid-cleaned slide. Three 

 drops of Liebermann-Burchard reagent (Huang et al. 1961) were placed over 

 the section, which was covered with a clean coverslip. A red filter was placed 

 below the condenser of the microscope, and the light intensity was adjusted 

 to a standard level at the source. The microscope was focused on the center 

 of the gland using the 20X objective (magnification = 200X); a "blank" 

 value was obtained by recording the light intensity reaching the camera. 

 Color development was completed in 30 min, and transmitted light was 

 recorded again at that time. A "Color Index" was then derived by subtract- 

 ing the blank value. 



Assuming a consistent effect of confinement for all animals, differences in 

 individual history would affect the animal's survival. Animals that have not 

 fed in the wild enter captivity already influenced by starvation, while well- 

 nourished animals begin their fasts only when placed in the experimental 

 enclosure. Patterns of change in monitored parameters are masked by this 

 asynchrony if plotted against "days in captivity"; this problem was elimi- 

 nated by plotting parameters against "days before death." 



In addition to nutritional differences, interindividual variation in 

 "normal" physiological and metabolic parameters in fishes has been noted 

 repeatedly (Srivastava 1970; Cordier, Barnoud, and Brandon 1957; Idler, 

 O'Halloran, and Home 1969; Burger 1967b; Denis 1922; Scott 1921; Hart- 

 man, Lewis, Brownell, Sheldon, and Walther 1941; Marsh and Gorham 

 1906). These effects were minimized by evaluating patterns through co- 

 variance analysis of the data. This method computed trends based on the 

 patterns of change for individual animals. These analyses were performed by 

 Mr. William Bell of the Cornell University Biometrics Department and re- 

 lied on programs of the Statistical Analysis System (A. J. Barr and J. H. 

 Goodnight, North Carolina State University). 



RESULTS 



Behavioral Observations 



Behavioral changes were both marked and stereotyped over the time in 

 captivity. Introduction into the pen was followed by a variable period 

 (minutes to hours) of inactivity. Mortalities were frequent over this period, 

 presumably from the stresses of capture and transport, since none of the 

 animals had obvious injuries. This period of inactivity preceded several days 

 of almost continual activity. The sharks swam strongly with infrequent 

 pauses on the floor of the pen; these "rests" were observed principally 

 during daylight hours. Blood samples taken at this time clotted rapidly. 

 Although no fighting was seen, scarring and torn fins were common at this 

 time; aggressive interactions probably occurred at night, when swimming 

 activity appeared to be more vigorous, but detailed observation was more 

 difficult. 



